A unified model for the G1/S cell cycle transition

Samuel Hume, Grigory L. Dianov, Kristijan Ramadan

Research output: Contribution to journalReview articlepeer-review

8 Citations (Scopus)


Efficient S phase entry is essential for development, tissue repair, and immune defences. However, hyperactive or expedited S phase entry causes replication stress, DNA damage and oncogenesis, highlighting the need for strict regulation. Recent paradigm shifts and conflicting reports demonstrate the requirement for a discussion of the G1/S transition literature. Here, we review the recent studies, and propose a unified model for the S phase entry decision. In this model, competition between mitogen and DNA damage signalling over the course of the mother cell cycle constitutes the predominant control mechanism for S phase entry of daughter cells. Mitogens and DNA damage have distinct sensing periods, giving rise to three Commitment Points for S phase entry (CP1-3). S phase entry is mitogen-independent in the daughter G1 phase, but remains sensitive to DNA damage, such as single strand breaks, the most frequently-occurring lesions that uniquely threaten DNA replication. To control CP1-3, dedicated hubs integrate the antagonistic mitogenic and DNA damage signals, regulating the stoichiometric cyclin: CDK inhibitor ratio for ultrasensitive control of CDK4/6 and CDK2. This unified model for the G1/S cell cycle transition combines the findings of decades of study, and provides an updated foundation for cell cycle research.

Original languageEnglish
Pages (from-to)12483-12501
Number of pages19
JournalNucleic Acids Research
Issue number22
Publication statusPublished - 16 Dec 2020


  • Cell Cycle/genetics
  • Cell Cycle Checkpoints/genetics
  • Cell Division/genetics
  • DNA Damage/genetics
  • DNA Replication/genetics
  • G1 Phase/genetics
  • Humans
  • S Phase/genetics
  • Signal Transduction/genetics


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